1. Field of the Invention
This invention relates to a blood gas control. More specifically, this invention concerns itself with a cell-free, stable, aqueous blood gas control containing a proteinaceous foaming agent; and a method for protecting environmentally sensitive fluids from atmospheric contamination.
2. Description of the Prior Art
Improvements in instrumentation have made the determination of blood pH, partial pressure of oxygen and partial pressure of carbon dioxide relative routine procedures for diagnoses of medical problems. Since vigorous therapeutic treatment is often dictated by such test results, the accuracy of such tests is essential. Accordingly, the use of control materials to verify the reliability of instrumentation used in such analysis is critical and necessary to provide an immediate indication of unexpected analytical deviation by the automated test equipment.
In the past, such control materials were not readily available and had to be prepared by the medical technologist immediately prior to performing the subject test. Generally, this involved adding known quantities of oxygen and carbon dioxide gases to a Tonometer containing a control fluid sample at a fixed pH. Gases in the liquid are equilibrated within the Tonometer and the an aliquot portion thereafter removed by the technician for use as a control for the blood gas instrumentation. Prior to the development of commercially available controls, the performance of blood gas analysis could only be performed in specially equipped laboratories engaged in research in the blood gas field.
Even where such controls are available, they had limited shelf life and readily undergo changes in dissolved gas concentration upon their exposure to the atmosphere. Where such controls have contained proteinaceous material, the problem of potential bacterial contamination was ever present and could cause decrease in the levels of dissolved oxygen and increase of levels of carbon dioxide. U.S. Pat. No. 4,001,142 describes a blood gas control essentially free of protein. While the control described in the '142 patent does provide an adequate control function, it does significantly differ from human serum which has an endogenous level of protein in the range of 6-8 grams per deciliter.
Under ideal conditions, control materials used in the verification of instrumentation performance should have essentially the same constituents as those present in the fluid which is to be subjected to analysis. Thus, protein free blood gas controls, while minimizing the problems of bacterial contamination and abbreviated shelf life, are significantly less preferred than those control materials which more closely approximate the endogenous complement of fluid to be analyzed.
Accordingly, it is the object of this invention to remedy the above as well as related deficiencies in the prior art.
More specifically, it is the principle object of this invention to provide an aqueous blood gas control having an acceptable shelf life and yet which approximates the composition of human serum.
Another object of this invention is to provide an aqueous blood gas control which is both stable during storage and yet maintains the concentration of dissolved gases at essentially their assigned value upon exposure to the atmosphere.
Additional objects of this invention include providing a method for isolation of atmospherically sensitive fluids from atmospheric contamination through the provision of a gas impermeable foam between the atmospherically sensitive fluid and the ambient environment.